Mismatch repair (MMR) is a conserved DNA repair process that is involved in post-replicative repair of mutated DNA sequences that occurs after genome replication. The process involves a group of gene products, including the mutS homologs GTBP, hMSH2, and hMSH3 and the mutL homologs hMLH1, hPMS1, and hPMS2 (Bronner, C. E. et al. (1994) Nature 368:258-261; Papadopoulos, N. et al. (1994) Science 263:1625-1629; Leach, F. S. et al. (1993) Cell 75:1215-1225; Nicolaides, N. C. et al. (1994) Nature 371:75-80) that work in concert to correct mispaired mono-, di-, and tri-nucleotides, point mutations, and to monitor for correct homologous recombination. Germline mutations in any of the genes involved in this process results in global point mutations, and instability of mono, di and tri-nucleotide repeats (a feature referred to as microsatellite instability (MI)), throughout the genome of the host cell. In man, genetic defects in MMR results in the predisposition to hereditary nonpolyposis colon cancer, a disease in which tumors retain a diploid genome but have widespread MI (Bronner, C. E. et al. (1994) Nature 368:258-261; Papadopoulos, N. et al. (1994) Science 263:1625-1629; Leach, F. S. et al. (1993) Cell 75:1215-1225; Nicolaides, N. C. et al. (1994) Nature 371:75-80; Harfe B. D., and S. Jinks-Robertson (2000) An. Rev. Genet. 34:359-399; Modrich, P. (1994) Science 266:1959-1960). Though the mutator defect that arises from MMR deficiency can affect any DNA sequence, microsatellite sequences are particularly sensitive to MMR abnormalities (Peinado, M. A. et al. (1992) Proc. Natl. Acad. Sci. USA 89:10065-10069). Microsatellite instability is therefore a useful indicator of defective MMR. In addition to its occurrence in virtually all tumors arising in HNPCC patients, MI is found in a small fraction of sporadic tumors with distinctive molecular and phenotypic properties that is due to defective MMR (Perucho, M. (1996) Biol. Chem. 377:675-684).
MMR deficiency leads to a wide spectrum of mutations (point mutations, insertions, deletions, recombination, etc.) that can occur throughout the genome of a host cell. This effect has been found to occur across a diverse array of organisms ranging from but not limited to unicellular microbes, such as bacteria and yeast, to more complex organisms such as Drosophila and mammals, including mice and humans (Harfe B. D., and S. Jinks-Robertson (2000) An. Rev. Genet. 34:359-399; Modrich, P. (1994) Science 266:1959-1960). The ability to block MMR in a normal host cell or organism can result in the generation of genetically altered offspring or sibling cells that have desirable output traits for applications such as but not limited to agriculture, pharmaceutical, chemical manufacturing and specialty goods. A chemical method that can block the MMR process is beneficial for generating genetically altered hosts with commercially valuable output traits. A chemical strategy for blocking MMR in vivo offers a great advantage over a recombinant approach for producing genetically altered host organisms. One advantage is that a chemical approach bypasses the need for introducing foreign DNA into a host, resulting in a rapid approach for inactivating MMR and generating genetically diverse offspring or sib cells. Moreover, a chemical process is highly regulated in that once a host organism with a desired output trait is generated, the chemical is removed from the host and its MMR process would be restored, thus fixing the genetic alteration in subsequent generations. The invention described herein is directed to the discovery of small molecules that are capable of blocking MMR, thus resulting in host organisms with MI, a hallmark of MMR deficiency (Peinado, M. A. et al. (1992) Proc. Natl. Acad. Sci. USA 89:10065-10069; Perucho, M. (1996) Biol. Chem. 377:675-684; Wheeler, J. M. et al. (2000) J. Med. Genet. 37:588-592; Hoang, J. M. et al. (1997) Cancer Res. 57:300-303). Moreover, host organisms exhibiting MI are then selected for to identify subtypes with new output traits, such as but not limited to mutant nucleic acid molecules, polypeptides, biochemicals, physical appearance at the microscopic and/or macroscopic level, or phenotypic alterations in a whole organism. In addition, the ability to develop MMR defective host cells by a chemical agent provides a valuable method for creating genetically altered cell hosts for product development. The invention described herein is directed to the creation of genetically altered cell hosts via the blockade of MMR using chemical agents in vivo.
The advantages of the present invention are further described in the examples and figures described within this document.